This isn't as bad as the other reviews make out, but there a few things you should now.
The place is a hotel called the Galleria, and from what we could make out, the staff had no idea we were coming. We had to convince them with our receipt and even email it on so they had any record of it.
We're not sure if the person running this Airbnb is the host, or just someone booking the room as a third party. Be aware of this, and have your details ready.
There was also a 300 bhat deposit on the keys. We had an early check out and were told that security is 24/7 and would take the keys off us and give us the money back when we leave. This was not the case. There was no sign of security when we left that night, and we waited for our taxi for around 20 minutes. We left our keys on their chair and left.
If you want a cheap, short term rental. It's a nice place, it's clean and convenient when it comes to getting around.
However, if you're looking for anything more, it's not your best bet. If we had a later check out, I'm sure things would've gone slightly more smoothly. For something cheap in Bangkok for a few nights, it's fine.